1. Technical Field
The present invention relates to an RF (radio frequency) MEMS (microelectromechanical system) switch device and its manufacturing method.
2. Description of the Related Art
MEMS switch device is a technology creating mechanical parts embedded in an electric switch device using semiconductor processing techniques.
When a switch is on, a MEMS switch device shows lower insertion loss than a semiconductor switch and when it is off, a MEMS switch device shows higher attenuation than a semiconductor switch. A MEMS switch device also needs less switch driving power than a semiconductor switch device. However, because an electrostatic attraction is proportional to the inverse of the distance between counter electrodes, the farther distance between counter electrodes becomes, the smaller electrostatic attraction does. Thus, a MEMS switch device requires more driving voltage with increased distance between counter electrodes. Here, an intersected area between a membrane electrode and a signal electrode, which generates electrostatic attraction, can be larger or a distance between a membrane electrode and a signal electrode becomes closer to reduce driving voltage. In this case, when a switch is off, electrical insulating characteristics can be lowered.
In addition, when charges are accumulated on a dielectric material between a membrane electrode and a signal electrode, stiction, which is adhesion phenomenon between a membrane electrode and a signal electrode, can be caused. Such a stiction phenomenon is intensified in proportion to driving voltage amplitude and an intersected area between a membrane electrode and a signal electrode.
Therefore, there is demand for MEMS switch devices operating at a low driving voltage and having small intersected area while maintaining a constant distance between a membrane electrode and a signal electrode.